2004 tailights on a 99 silverado

Hey guys I really want to put on some 2004 tail lights on my truck. It is a 99 silverado, Can somebody please tell me what I have to do to my truck to make it fit. What I need, how hard it is, and maybe even some step by step instructions would be great...thanks guys!

To get the lights to fit, all you have to do is bolt them in. Now here's the tricky part. 03-04 lights have an extra bulb down in the bottom of the lamp. In order for this to work, you either have to get the 03-04 lights w/ the harnesses, or either splice a wire into your existing harness. If you don't, you'll have a hole in the light w/no light in it. I'm not sure where to splice it yet, but from what I've heard, its very easy.